The invention relates to needle valves and more particularly to needle valves for adjusting carburetors.
The use of plastic in making carburetor needle valves is known. A problem encountered with the use of plastic materials in such an application includes the tendency of plastics to creep under application of heat, thereby reducing the precision of the tolerances to which the plastic elements are manufactured. Another problem with the use of plastic materials in a carburetor needle valve arises in the use of a metal valve member in conjunction with a plastic valve seat. During calibration of the carburetor, the metal needle valve member often engage the plastic valve seat under excessive pressure, thereby damaging the needle as well as the seat. This damage results in waste of damaged valve seats and needles. In addition, the cost of manufacturing highly precise, machined parts is increased by the prospect of waste due to damage.
Attention is directed to U.S. Pat. No. 4,568,499 which, issued to Wood on Feb. 4, 1986 and which is assigned to the assignee hereof.